(1) Field of the Invention
The invention relates to processes for the assembly line manufacture of articles and more particularly to the timely and orderly delivery of a plurality of small hardware components during the assembly of complex articles containing mechanical components.
(2) Background of the Invention and Description of Previous Art
It is well known that the productivity of an assembly line is strongly dependent on the timely and orderly delivery of components of the article being manufactured to the appropriate various stations of the assembly line. Complex articles containing electronic and mechanical components, such as computer storage disk drives, compact disc drives and the like, have additional assembly requirements, which include high degrees of cleanliness, ambient control, and careful handling of components.
Computer drives of all sorts typically consist of a mechanical drive mechanism to which at least one printed circuit board is attached and electrically connected. In the manufacture of these drives, the printed circuit board is typically populated with electronic components, on a placement machine which uses robotic arms to pick, place, and solder the components. Placement machines have a very high and flawless placement rate. On the other hand, the mechanical sub-assemblies to which printed circuit boards are connected, still require manual assembly by a line operator. The mechanical sub-assemblies utilize a plurality of small hardware parts such as screws, nuts, pins, gears, springs, micro switches, bearings, and the like which must be selected, oriented and then placed by an operator in a specified sequence. Finally, the mechanical sub assembly and corresponding printed circuit board(s) are manually assembled and mounted on a chassis and encased. These manual assembly operations are highly operator dependent and greatly limit productivity and reliability yield of the finished product. While limited volume and multiple part number considerations do not make total robotic assembly cost effective, it is nevertheless desirable to streamline the process by reducing the time spent by the operator in selecting, sequencing, and orienting the small hardware components on the assembly line. The present invention provides a method for accomplishing such a procedure and thereby improves the overall productivity as well as the reliability of the finished product.
For the purpose of the present invention small hardware is defined as mechanical components which individually weigh less than about 200 grams and have a longest dimension of less than about 10 cm. Articles fitting this definition include but are not limited to pins, gears, springs, studs, spacers, micro switches, nuts, bolts, screws, and bearings. Further, for the purpose of present invention, the definition of small hardware also excludes articles which are spherically shaped and which, being totally symmetric, do not require orientation for installation.
Conventionally, small hardware is packed randomly and arbitrarily in bags, boxes, or trays. The operator must first pick up a piece of hardware, by hand, determine its orientation, either visually or by feel, then orient it for installation, and finally install it on the assembly. These operations are not only time consuming but are also stressful to the operator, both physically and mentally, particularly under pressure of time. Further, hardware items packed loosely tend to rub against each other in handling, thereby not only causing damage to the item but also creating particulate debris, which in highly critical clean conditions, can seriously affect the reliability of the final product. The method and means of presentation of small hardware to the assembly line operator described by the present invention specifically addresses these issues and not only streamlines the manual assembly but also eases the burden on the line operator. Further, the method of the invention brings the small hardware installation a step closer to an automated process with minimal additional cost. This is due mainly to the ability to prepare the parts for presentation off-line.
Ames, U.S. Pat. No. 5,887,727 cites a method and means for sorting and funneling small hardware by the use of screens which are manually operated. The screens can be designed to parallel align and transport cylindrical objects such as pins or springs. However, an additional operation may be required to align screws with all the heads in one direction. Labat, et. al., U.S. Pat. No. 6,158,585 shows a dispenser of screws to an assembly line wherein a set of small hardware, notably of screws, all of the same type and size, is packaged on a holder consisting of a thin compartmented card having a lower break-away foil and covered with a transparent plastic layer in the form of a blister pack. Each holder is labeled and multiple holders, all consisting of the same screw, are prepared, and loaded into a cartridge which, in turn is loaded into a dispensing cabinet off-line. The holders are then manually extracted on-line, one at a time, through an opening in the bottom of the cabinet. If more than one type of screw is used, each screw type is packaged in its own cartridge and cabinet. Thus each dispensing cabinet, provided to the line assembler, contains only one type of screw.